The present invention relates to a magnetic bubble replicator which uses a soft magnetic material element and a hairpin-shaped conductor, in a magnetic bubble memory.
A prior art magnetic bubble memory uses a magnetic bubble replicator to assure non-volatility of the magnetic bubble memory. The replicator has a function to divide a magnetic bubble in a minor loop group stored as information into a magnetic bubble to be transferred to a detector for detection and a magnetic bubble to be retained in the minor loop group as the information.
A magnetic bubble memory of a block replicate scheme which uses replicators each for making a copy of magnetic bubble of a minor loop onto a major loop, has been known (U.S. Pat. No. 3,810,133).
In a magnetic bubble memory of a two-major line-minor loop group scheme as shown in FIG. 1, it is common to use replicators 7 as gates between a readout major line 8 and minor loop groups 6. In FIG. 1, numeral 1 denotes a biasing magnetic field applied perpendicularly to a surface of a magnetic thin film for retaining magnetic bubbles in the magnetic thin film, numeral 2 denotes a rotating magnetic field applied by a driving coil for driving the magnetic bubbles, numeral 3 denotes a bubble generator, numeral 4 denotes a write major line, numeral 5 denotes a swap gate and numeral 9 denotes a bubble detector.
In the magnetic bubble memory of the above type which uses a soft magnetic material, a replicator including a soft magnetic material element 12 and a hairpin-shaped conductor 10 as shown in FIG. 2 is used (U.S. Pat. No. 4,012,726). It is called a sideway replicator and fully utilizes an anisotropy of a pattern shape.
A magnetic bubble memory which uses the soft magnetic material (primarily permalloy) so far put into practice uses magnetic bubbles of 2 .mu.m in diameter. Thus, a sufficient operation margin is provided by the sideway replicator.
The present inventors manufactured a replicator for the magnetic bubbles of 1 .mu.m in diameter based on the above-mentioned sideway replicator and examined an operation characteristic. The result is shown in FIG. 3, in which an abscissa represents a strength of a rotating magnetic field to drive the magnetic bubbles and an ordinate represents a biasing magnetic field margin or an allowable range represented by percentage to a center of the allowable range, which is a range allowed to a biasing magnetic field applied perpendicularly to the magnetic thin film of the magnetic bubble chip to vary without causing an error in the magnetic bubble chip. When the rotating magnetic field is 60 Oe, the biasing magnetic field margin is 10% but when the rotating magnetic field is 50 Oe, the biasing magnetic field margin is 8%. This causes a problem in practical use.
It was found by the present inventor's experiment that a cause of the reduction of the biasing magnetic field margin is that, as shown in FIG. 4, a magnetic bubble 13 is not propagated through a crossing area of an upper side 12a of the soft magnetic material element 12 and the hairpin shaped conductor 10 and it is rebounded as shown by an arrow R.